A pixel circuit for an organic light emitting display includes first, second, third, fourth, fifth, and sixth MOS transistors, a first capacitor, and an organic light emitting diode. The gate electrode of the first MOS transistor receives a first scanning signal. A first electrode of the first MOS transistor receives a data signal. The gate electrode of the third MOS transistor receives a third control signal. The gate electrode of the fourth MOS transistor receives the first scanning signal. The gate electrode of the fifth MOS transistor receives a first control signal. A first electrode of the fifth MOS transistor receives a reference voltage. The gate electrode of the sixth MOS transistor receives a second scanning signal. The first electrode of the sixth MOS transistor receives the reference voltage.